Biogenesis and function of IgM: The role of the conserved μ-chain tailpiece glycans

Claudia de Lalla, Claudio Fagioli, Franca Serafini Cessi, Daniela Smilovich, Roberto Sitia

Research output: Contribution to journalArticlepeer-review

Abstract

The tailpiece of secretory Ig-μ-chains (μ(s)tp) is highly conserved throughout evolution: in particular, a carboxy-terminal cysteine residue (Cys575) and a glycan linked to Asn563 are found in all species sequenced so far. Here we show that the μ(s)tp oligosaccharide moieties are important for the binding of J-chains and for the process of IgM polymerization. In the absence of the μ(s)tp glycans, pentamers cannot be assembled and polymers containing six or more subunits are secreted. Despite their increased valency, these molecules have a lower association rate with antigen than wild-type polymers. Unexpectedly, the C-terminal oligosaccharides also affect kinetic parameters on unpolymerized subunits. Thus, monomers lacking the C- terminal sugars because of either site-directed mutagenesis or selective enzymatic deglycosylation with endoglycosidase H, have a lower k(on) for the antigen. Taken together, our results indicate that the C-terminal μ-chain glycans can shape the structure of μ(s2)L2 subunits and their further assembly into polymers.

Original languageEnglish
Pages (from-to)837-845
Number of pages9
JournalMolecular Immunology
Volume35
Issue number13
DOIs
Publication statusPublished - Sep 1 1998

Keywords

  • Affinity
  • Glycosylation
  • IgM
  • Polymerisation
  • Secretion

ASJC Scopus subject areas

  • Molecular Biology
  • Immunology

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